Circuit breaker



June 21, 1938. K. RQNISBET 2,121,441

CIRCUIT BREAKER Filed Nov. 21, 1936 s Sheets-Sheet 1 FIG- 2. a A

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June 21, 1938. R NlsBET 2,121,441

C IRCUIT BREAKER 3 Sheets-Sheet 2 Filed Nov. 21, 1936 mwuik QM \NVLNTOR- Patented June 21, 1938 UNITED STATES CIRCUIT BREAKER Kenneth R. Nlsbet, Washington, D. 0.

Application November 21, 1936, Serial No. 112,151

11 Claims.

This invention relates to a circuit breaker oi moderate rating, suitable for use in the control of lighting circuits and comparatively small power applications and that is automatically op- Another object of the invention is to provide a circuit breaker that is interchangeable with many types of tumbler switches already installed, and one that is operated as a tumbler switch in that there is no neutral position of the operating handle, with the attendant disadvantagesthereof.

A still further object of the invention is to provide a circuit breaker having inverse time overload trip characteristics with the advantages of an ordinary tumbler switch thus combining some of the merits of both.

Other objects and advantages of the invention will be apparent in the description following hereinafter.

With reference to the accompanying drawings:

Fig. 1 is a plan view, partly in section, of the circuit breaker installed within an ordinary sectional type flush mounted outlet box.

Fig. 2 is an elevation taken along line aa 01' Fig. 1, showing the circuit breaker in the closed position.

Fig. 3 is a part elevation, showing certain elements of Fig. 2, with the circuit breaker in the normal opened position.

Fig. 4 is an isometric drawing of the carrier assembly drawn to a larger scale, in a position approximately midway between the opened and closed positions, drawn for the purpose oi clari-" fication.

Fig. 5 is a section thru Fig. 4, with the side plates and spring members added.'

Figs. 6 and 7 are part sections thru the operating and contact carrier heads showing the relative positions of the pawl, in thecircuit breaker opened and closed positions respectively.

Fig. 11 is an alternate form of a bimetallic thermal element.-

Fig. 12 is an alternate form of contact between the thermal element and the circuit breaker releasing device.

Figs. 13 and 14 are drawings in part showing a multi-pole circuit breaker having separable contacts.

By reference to Fig. 1, the numeral l represents a standard sectional conduit type outlet box, commonly used for wall switches and receptacles, in which the circuit breaker is installed. The use of this particular type of outlet box is not restrictive inasmuch as the common switch boxes or fittings in general usage can be utilized equally 15 as well, which includes gang and gangable switch boxes or special boxes. The mechanism is contained within housing 2, having paper or fibre insulation 2a over the top, which is constructed of an insulating material and which has one my removable side 3 for assembly purposes. The housing is secured to the outlet box and covered in a manner similar to that used for ordinary tumbler switches, by means of yoke l and cover plate 5. The mechanism is in general supported in a frame 8 consisting essentially of stop bar 1, pin 8, shafts 9, III, II, and two identically constructed side plates, only one 12 of which is shown on the drawings, the other side plate l3 being similarly located with respect to the horizontal axis and is so designated in Fig. 2.

It is to be noted that pin 8 extends into-both sides of housing 2 thru side plates I2 and I3, to form a pivot for frame 6 which has a small angular movement, to be described hereinafter. It should also be noted that stop pin it and trip pin [5 extend into both sides of housing 2 and are rigidly secured in place.

The carrier assembly shown in Figs. 4 and 5 consists of two units, one an operating carrier it having a radially curved head ll, a supporting leg IS, the end of which is formed to provide a means for an axis to coincide with that of head H, the said end being provided with a guide 19 mechanically secured thereto, one edge of said end being cut away or otherwise formed to provide catch 20 which is utilized in connection with the tripping mechanism as covered hereinafter. Head I! has operating handle 2| mechanically secured thereto and which is of an insulating material, the mechanical attachment likewise furnishing the means of support for spring 22 which is biased to the curvature of head l'l to hold pawl 23 in a normally closed position. Pawl 23 is movable with shaft 24 which in turn is supported by bearings 25 and 28 formed by proiections from head i1. The other unit of the carrier assembly is contact carrier 21 which has a radially curved head 23 but of a smaller radius than that of head l1, and formed in a manner such that one operates within the other, a supporting leg 23, which is drilled to support the electrical contacts as described hereinafter, and has its end similarly formed but in the opposite manner to catch 20, to provide catch 38, and has guide 3| mounted thereon. Fig. 5 is a cross-section of Fig. 4, at right angles thereto, and shows the relative positions of plates l2 and I3 to operating carrier l6 and contact carrier 21. Spring elements 32 and 33 are mounted about their respective guides I3 and 3|, their outer ends being secured to plates i2 and I3, their inner ends being in contact under tension to legs l8 and 23 thereby biasing both operating carrier i5 and contact carrier 21 to their normal positions in which the circuit breaker is open. Washer 34 is merely a separating means and an assistant for maintaining alignment of its adjacent parts. Shaft 9 is the common support for carriers l6 and 21.

Part plan views of the pawl ends of heads l1 and 23 are shown in Figs. 8 and 9 respectively. Head I1 is projected on both sides, which pro jections are formed to provide bearings 25 and 28 while the top inner edge 35 is flat beveled to form a bearing surface for the extreme tip of pawl 23. Head 28 has a longitudinal slot 38 near the end with a rounded or beveled portion 31 between the slot and the end.

To open the circuit breaker manually, the following operation is described, with particular reference to Figs. 2, 4 and 5:-A counterclockwise force is applied to handle 2| which force is transmitted thru leg l8 to shaft 8 thence to frame 8 thru side plates l2 and I3. The aforesaid force acting thru the described linkage causes frame 5, with all its subioined parts, to rotate counterclockwise thru a small angle about pin 8 against thebias of spring 38. In this angular movement, projection 38 of latch-lever 48 is brought into contact with trip pin I5, which being stationary within housing 2, causes the aforesaid latch-lever 40 to rotate about its shaft H) which movement in turn causes tip 4| to be tripped from catches 23 and 38 thus releasing both the operating car rier l8 and contact'carrier 21 which being under bias from springs 32 and 33 quickly rotate to their normally open position as shown in Fig. 3. Mercury contact element 42 being secured to leg 23 is tilted to an of! position whereby the mercury 43 within the container flows by gravity away from electrodes 44 and 45, thus breaking the electrical circuit. In the first part of this operation as operating carrier l6 and contact carrier 21 are tripped, frame 8 is returned to its normal position with side plates 12 and i3 in contact with stop pin l4, by virtue of the tension in spring 38.

Fig. 10 shows the relative positions of the trip and terminal assembly, consisting essentially of thermal element 48, latch-lever 48 on its shaft l0, spring member 48, trip pin l5, terminals 45b, 48c and 48d. The action is described as follows: Current from the external source enters the assembly thru wire terminal 48c, ilows thru both legs of thermal element 48 to terminal 48d thence by flexible connectors, which are not shown, to the mercury contact element, thence back to wire terminal 46!) to complete the circuit. If the current is excessive, the free end 45a is deflected which movement is transmitted thru insulator 41 to rotate latch-lever 40 on or about its shaft in, to trip the circuit breaker as described elsewhere herein. Spring member 48 normally holds latchlever 40 approximately parallel to thermal ele-- ment 46.

Automatic operation of the circuit breaker due to excessive current takes place in the following manner, reference being made to Figs. 2, 3 and 4: Current in excess of a predetermined figure thru bimetallic element 45 causes the free end 480. to deflect in the usual manner. This movement is transmitted thru insulating pin 41 to projection 48 of latch-lever 40 thereby rotating the same on or about its shaft in against the bias of spring element 49 moving tip 4| from faces 28 and 38 thereby releasing operating carrier 18 and contact carrier 21 to their open positions as noted hereinbefore. Mercury contact element 42 being secured to leg 28 of contact carrier 21 breaks the electrical circuit in the manner noted above. The circuit being thus interrupted, current ceases to flow and thermal element 46 gradually resumes its normal position due to the cooling effect. In the tripped position of the circuit breaker, projection 33 of latch-lever 48 is in contact with the radially curved ends of legs I8 and 28 and is under bias from spring element 49. It is to be noted that with the circuit breaker in the tripp d position, projection 58 of latch-lever 48 is in a position to strike pro- Jection 5| of pawl 23 upon reclosure of the cir cuit breaker unless the free end 46a of thermal element 48 is in its normal position, thus preventing immediate reclosure following a severe overload.

Fig. 6 shows the relative positions of pawl 23, heads i1 and 28 when the circuit breaker is open. Upon the approach to the open position, contact carrier 21 is first stopped followed by operating carrier is as their respective heads 28 and I1 strike stop bar 1, as noted in Fig. 3. Pawl 23 moves with head I1 by virtue of its mounting, and projection 52 being biased by spring 22 impinges and rides over rounded surface 31 falls into slot 36 and thereby engages head 28 which in turn causes carrier Hi to be latched to carrier 21 for the closing operation.

To close the circuit breaker, a clockwise force is applied to operating handle 2| to move carrier I8, hence carrier 21, hence mercury contact element 42 in the same direction about shaft 8. With thermal element 48 in its normal position, the above described rotation is continued until portion 53 of pawl 23 strikes stop pin H which action rotates pawl 23 to release head 28, hence carrier 21, permitting the motion of said carrier 21 to be reversed, which reverse motion is arrested as tip 4| engages face 38. Upon the release of handle 2i, carrier l8 moves counterclockwise thru a small angle until face 20 is similarly engagedv by tip 4|. Mercury contact element 42 now being in a horizontal position, mercury 43 surrounds both electrodes 44 and 45 to close the electrical circuit. If thermal element 45 is in an abnormal position, projection 58 interferes with the clockwise motion of pawl 23, trips the same as projection 5| strikes projection 58 which prematurely releases head 28 hence carrier 21 hence mercury contact element 42 to prevent reclosure of the circuit breaker electrical contacts.

Fig. 7 shows the relative positions of pawl 23, heads l1 and 28 when the circuit breaker is closed. It is to be noted that the said heads I! and 28 are disengaged as projection 52 rests upon surface 3'! beyond slot 36.

It is to be noted that by the use of mercury contact element 42, the circuit breaker is successfully operable only when installed in a vertical position. To avoid this requirement, I propose to utilize separable contacts in lieu of the said mercury contact element, for single or multipole service, as is indicated in Fig. 13. The use of such separable contacts will permit increased current ratings thus permitting a wider range of the circuit breaker utilization.

The design, type and location of spring member 38 is that of 'a preferred example but it is not to be so restricted as to exclude the use of another member of different design, type or location to serve the same purpose, that of maintaining frame 6 in its normal position within housing 2.

The U-shaped bimetalic' thermal element 46 noted in Fig. 10 is not necessarily that of a preferred example inasmuch as an elongated element of the bar type, or one of the type indicated in Fig. 11 may be utilized, with modifications in the wire terminal arrangement on housing 2.

It is not intended that the curvature of tip 4| or the angularity and respective lengths of catch faces 20 and 36 be restricted to the design shown on the drawings inasmuch as with modifications thereof and with consideration given the lengths of the lever arms and spring members involved, the sensitivity of the tripping arrangement can be reasonably governed, an important factor when dealing with comparatively low current values.

Fig. 11 shows an alternate form of a bimetallic thermal element consisting of an elongated portion of thermostatic metal or of dissimilar metals generally utilized for such purposes, having a terminal means 54 at each end. A raised portion 55 is provided along the center line of the element, in order to add rigidity to the unit, which may be formed in either of the metals or both.

Latch-lever element 40 is constructed preferably of an insulating material but is not to be so restricted inasmuch as it may be of metal of a slightly different form.

Insulating pin 41 may be eliminated by incorporating its function in another projection 41a to latch-lever 40 as is indicated in Fig. 12, which serves to eliminate any intermediate element between latch-lever 4'0 and thermal element 46.

Figs. 13 and 14 show a part assembly of a multi-pole circuit breaker in which the various elements covered hereinbefore are incorporated latching elements, pins, stops, shafts and housing similar in functions to these previously described but modified for a multi-pole arrangement with separable contacts and to be utilized in connection with standard gang outlet boxes or end of spring member 65 on the other end of which is secured insulator 66 which has mounted thereon contacts 61, 68, 69 arranged to provide wire terminals for the fixed ends of thermal element terminals 10, H and 12, the latter not being visible in the drawings, by means of flexible conductors 13, there being one such per thermal element. Insulating barriers 14 are provided between adjacent pole terminals and one bar type thermal element 15 is provided per pole. Latchlever 16 has secured thereto, or an integral part thereof, plate 1'! which extends across the free ends of all thermal elements 15 in order to receive the motion of either one or all said thermal elements upon an electrical overload. Stationary contacts 16, I1 and 18 extend thru housing 56 to provide one set of wire terminals 19. Flexible conductors 80 connect the free ends of thermal elements 14 to the other set of wire terminals 8|.

Operation of the circuit breaker, either manually or automatically, so far as linkages of mechanical parts are concerned, is as described hereinbefore. Automatic operation from a. closed to an open position is described in part as follows: Current in excess'of its rating will, in one or more thermal elements either individually or collectively, cause the same to deflect against plate 11 thus rotating latch-lever .16 on or about shaft 82 which trips legs 58 and 59 to their normally biased positions, thereby quickly rotating block 64, spring member 65, insulator 66 with contacts 61, 68, 69 all in a counterclockwise direction thus breaking the electrical contact with stationary contacts I6, l1, 18 to interrupt the electrical circuit.

Spring member 65 is so utilized with the forms of contacts noted to permit some latitude due to the movement of the frame in the manual opening operation. With knife contacts in lieu of buttons, block 64, member 65 and insulator 66 may be of unit construction or member 65 may be rigid.

It is to be understood that the forms of this invention herewith shown and described are to be taken as preferred examples of the same, and that various changes in the shape, size and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

Having thus described the invention, I claim:

1. In a device of the class described in combination, a means responsive to a predetermined circuit condition for interrupting a circuit and manually operable to either close or interrupt said circuit, consisting of an insulating housing; a movable supporting member; an operating element; a switch element; a releasable latch element for connecting said operating element to said switch element thru the closing cycle; a. means fixed to said housing for tripping said latch element; a separate biasing means for each item listed above, that is to say, the supporting member, the operating element, the switch element, and the latch element; a releasable latch-lever element for locking said operating element and said switch element in a closed position; a biasing means for said latch-lever element; the said latch-lever element being pivoted and releasable by a, fixed means to rotate the said element about its axis in the manual opening operation and by a thermal element in the automatic operation, the said latch-lever element having two projections, one one either side of its said axis to provide for the'said rotation and still another projection arranged to intercept said releasable latch element to prevent reclosure unless the said thermal element is in approximately its normal position; the said switch element having a means for mounting one or more contacts thereon.

2. In a device of the class described in combination, a means responsive to a predetermined circuit condition for interrupting a circuit and manually operable to either close or interrupt said circuit, consisting of an insulating housing; a movable supporting frame; an operating element; a switch element; a releasable latch element for connecting the said operating element to the said switch element thru the closing cycle; a fixed means for tripping said latch element, the said means being fixed to said housing; a biasing means for each oi",--the said frame, the said operating element, the said switch element, the said latch element; a releasable latch-lever element for locking said operating element and said switch element in a closed position; a biasing means for said latch- -lever element; the said latch-lever element being pivoted and releasable by a means fixed to said housing to rotate said element about its axis in the manual opening operation and by a thermal element in the automatic operation, said latch-lever element having two projections, one on either side of said axis to provide means for said rotation and still another projection arranged to intercept said latch element unless said thermal element is in its approximately normal position; said switch element having a plurality of contacts mounted thereon.

'3. In a device or the class described in combination, an operating means; a switch element; a biased releasable latch for connecting said switch element to said operating means thru the closing cycle; a tripping means embodying a bimetallic thermal element; a biased releasable latch element for holding said switch element in a predetermined position and Ior tripping said switch element under a predetermined circuit condition, said latch element being pivotcd and movable about an axis centrally located and having one projection moving generally in the same direction with the free end of said thermal element, another projection moving in the opposite direction and still another projection moving generally at a right angle to that of the free end of said thermal element, one said projectidn operating in connection with said switch element, another said projection operating in connection with said thermal element and the other said projection operating in connection with said releasable latch; an insulating housing provided with terminals.

4. In a device of the class described in combination, a main supporting element within an insulating enclosure; an operating means embodying a biased pivoted member having an insuiating operating handle affixed thereto; a switch member having a mercury contact element attached thereto; a biased pivoted releasable means for latching said operating means to said switch means, said releasable means having a projection thereon for said latching purpose, another projection arranged to impinge against a fixed element within said enclosure thereby rotating said releasable means at or near the closed position and thus releasing said switch memberjromsaid operating means. said switch member and said operating member thereby moving to their iully opened positions ready for reclosure; a tripping means embodying a biased releasable latch for retaining both said operating means and said switch member in the closed position; a bimetallic thermal element for operating said tripping means.

5. In a device of the class described in combination, a biased carrier assembly embodying an operating means and a switch element having attached thereto a contact assembly; a tripping assembly embodying essentially a releasable latch and a bimetallic thermal element, the said thermal element being arranged to transmit a movement therefrom due to excessive current, directly to said releasable latch, said latch being biased and serving a purpose of retaining said carrier assembly in a closed position, one projection of said latch moving generally in the same direction as the free end of said thermal element, one projection moving in the opposite direction and another projection moving approximately at right angles to the direction of movement of said thermal element end.

6. In a device of the class described in combination, a main supporting element Within an insulating enclosure; an operating means embodying a biased pivoted member having arr-insulating operating handle affixed to the head thereof; a switch member having a contact assembly attached thereto and movable about an axis common with that of the said pivoted memher; a biased releasable means for latching said operating means to said switch member, supported by a pivoted means from said head of the aforesaid pivoted member; the said releasable means having a projection therefrom for the i said latching purpose and another projection arranged to impinge against a fixed element within the said insulating enclosure in order to rotate said releasable means about its pivot to release said switch member from said operating means essentially at the closed position; a tripping means embodying a biased releasable latchlever element for retaining both the said oper-- ating means and said switch member in the closed position by the engagement of one projection on said latch-lever element against catch faces on the pivoted ends of said pivoted memher and said switch member; a bimetallic ther- .mal element for automaticallyv operating said tripping means.

'7. In a device of the class described in combination, a main supporting element within an insulating enclosure; an operating means; a switch element having a biased member pivoted about an axis coinciding with "that of the said operating means and having secured thereto a contact assembly; the said switch element operating in planes parallel to and opposite said operating means and operatively connected to said operating means thru the closing cycle only by means of a releasable latch element; a tripping assembly embodying essentially a bimetallic thermal element, a releasable latch-lever element for locking said operating means and said switch element in the closed position, said latchlever element having a projection to provide the said locking arrangement, another projection to contact said thermal element for automatic tripping and still another projection to trip the aforesaid releasable latch element in order to release said switch element from said operating means prior to the normal closed position of the said switch element to prevent reclosure against overload; said thermal element being of the bar type having terminals at each end thereof.

8. In a device of the class described in combination, a main supporting element within an insulating enclosure; an operating means; a switch element consisting of a biased member pivoted about an axis coinciding with that of the said operating means and having secured thereto a contact assembly; the said switch element operating in planes parallel to and opposite said operating means and operatively connected to said operating means thru the closing cycle by means of a releasable latch element; a tripping assembly embodying essentially a bimetallic thermal element, a releasable latch element for looking said operating means and said switch element in the closed position, said releasable latch means having a projection therefrom to provide the said locking arrangement, another projection to contact said thermal element and still another pro- .iection to trip said releasable latch element to release said switch element from said operating means prior to the normal closed position of the said switch element.

9. In a device oi the class described in combination, an insulating enclosure; a biased pivoted frame element; a biased switch element for -'opening and closing the circuit; a means for operating said switch element, said means being operatively connected to said frame element; a tripping assembly embmying a bimetallic titerrnal element; a biased controlling element operated by said thermal element, the said controlling element latching said switch element in the closed position and provided with a means to prevent said switch element beingclosed imme diately following a severe overload, and being of unit construction having a circular movement about an axis and operatively connected to said irame element; said thermal element being of the bar type having a terminal means at each end thereof. 4

iii. In a device of the class described, in combination, an insulating housing; a frame consisting of two plates similar in design and purpose,

held apart by a plurality of separating means to form a nesting for a carrier assembly, the said frame being pivoted and biased to a predetermined position, said position being determined by an element fixed to said housing, against which element a projection on each said plate is in normal contact by virtue of the said biasing means; said carrier assembly embodying an operating member and a switch member having a contact assembly mounted thereon; a tripping means embodying a bimetallic thermal element and a latch-lever clement, said latch-lever element being supported by the said frame and movable with said frame in its angular movement; a biasing means for said latch-lever element; said latch-lever element'serving the purpose of locking said operating element and said switch element in a closed position and an additional purpose of preventing the final closing operation of the said switch element unless the said thermal element is in its near normal position; a means for tripping said latch-lever element independent of said frame; the said insulating housing being provided with wire terminal means.

11. In a device of the class described, a circuit breaker having a slow-make quick-break mechanism, embodying an operating element; a car rier element for electrical contacts, operatively connected with the said operating element during the closing cycle and latched thereto in the open position; said operating element and said carrier element each being biased and both supported by a common shaft fixed within a pivoted frame; a tripping assembly embodying in part a bimetallic thermal element; an insulating housing provided with wire terminals; said mechanism providing a means to quickly open said electrical contacts upon a predetermined circuit condition and to permit a manual re closure with a slow motion in said carrier element.

KENNETH R. NISBET. 

